6.1.2.3.3 DC and Schema/Config NC Replicas
Every DC is instructed to host the schema and config NC replicas.
A DC is hosting the schema and config NC replicas when the following are true:
The attribute msDS-hasMasterNCs and attribute hasMasterNCs on the nTDSDSA object representing the DC contain the DSName of both the NC roots representing the schema and config NCs.
The attribute msDS-HasInstantiatedNCs on the nTDSDSA object representing the DC contains two Object(DN-Binary) values such that the DN fields are the DSName of the NC root representing the config and schema NCs, and the binary fields contain the values of the instanceType attribute on the config and schema NC root objects on the DC.